Induction of Experimental Arthritis in Balb⁄C Mice by Inclusion of a Foreign Protein in the Collagen Inoculum (1).
Susceptibility to CIA has been associated with the expression of certain major histocompatibility complex (MHC) class II molecules. Mouse strains expressing the class II molecule I-Aq (e.g., DBA ⁄ 1 and B10.Q) or I-Ar (e.g., B10.RIII) have been shown to be the most susceptible strains. Mice expressing the class II molecule I-Ad (e.g., Balb ⁄ C) or I-Ab (e.g., C57BL ⁄ 6) are regarded as resistant strains.
Balb⁄C mice were immunized twice, three weeks apart, with BCII or BCII mixed with OVA in CFA containing 5 mg killed M. tuberculosis per ml. The mice that were immunized with BCII alone failed to develop clinical arthritis. Instead, animals immunized with BCII mixed with OVA developed progressive arthritis with high incidence.
Histological analysis of the joints in the hind limbs showed typical features of arthritis in all co-immunized mice but not in mice that were immunized with BCII alone.
Co-immunized animals developed clinical arthritis if the mixture of BCII and OVA was emulsified in CFA but not if the same mixture was emulsified in IFA. Mice that were immunized with a mixture of BCII and KLH developed clinical arthritis with high incidence, whereas immunization with BCII and MSA did not lead to arthritis.
The levels of IgG, IgG1, IgG2a and IgG2b anti-BCII antibodies in serum were significantly higher in coimmunized mice than in mice immunized with BCII alone on one week after the booster immunization. If BCII and KLH were injected at separate sites the serum IgG anti-BCII antibody activity remained at the same low level as in mice that were immunized with just BCII.
The BCII-specific proliferation was similar, regardless of immunization protocol, in cultures of splenocytes collected from Balb ⁄ C mice. The splenocytes did not secrete IFN-g in response to BCII stimulation in vitro.
Environmental factors such as health status, stress and behaviour beside genetic factors such as the MHC haplotype contribute to CIA susceptibility. For instance, inter-male aggressiveness enhance responsiveness to CIA. Thus, differences in the stability of the social structure might explain the observed temporal discrepancy between our experiments. The KLH and BCII molecules aggregate or are in such close vicinity to each other that they are endocytosed together by the same BCII-specific B cell. Hence, both molecules are degraded and presented as peptides on class II MHC molecules on the same anti-BCII-specific B cell. This would make it possible for KLH-specific T cells to help the anti-BCII-specific B cell to produce anti-CII antibodies.